Fatigue behaviour of geomaterials under cyclic environmental loading

循环环境荷载下岩土材料的疲劳行为

• 批准号: RGPIN-2020-03949
• 负责人: Wong, Ron
• 金额: $ 2.26万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=749445
• 关键词: Fatigue; behaviour; geomaterials; under; cyclic

Cyclic loadings are commonly encountered in engineering applications. Wind exerts dynamic loads on tall buildings. Wave and ice load imposes threat to offshore structures and transportation infra-structures in arctic waters. Seasonal variation of precipitation and water table imposes repeated loads on earthworks. Cyclic freezing-thawing of ground along with traffic loads affect the long-term performance of pavements and buried utilities. Natural geohazards such as earthquakes and landslides are cyclic and dynamic in essence. Mineral mining and oil and gas extraction also involve cyclic loading to the surrounding environment. The long-term objective of this proposed research program is to develop techniques to quantify fatigue behaviour and expected life span of different geomaterials under cyclic loading encountered in the field so that new technologies can be developed for prevention of hazards, protection of the Environment, and optimization of material life span and natural resource recovery. The first type of geomaterials studied in this proposed research is Montney Formation which is one of the major natural oil and gas resources in Canada. Due to its tight pore structure, hydraulic fracturing (HF) has been used for exploitation of this resource. It involves high-pressure injection of chemically treated fluid into the formation to create a fracture network enhancing oil and gas production. Potential risks to natural water sources by contamination of fracture fluid and hydrocarbons resulting from hydraulic fracturing have raised public concerns. Hydraulic fracturing also induces seismic events which may impose detrimental effects on surface facilities. There is an urgent need to modify the current HF treatment to enhance the hydraulic flow in this tight material and reduce the amount of seismic energy released from the treatment. We propose to unlock the tight material by failing it in a controllable "fatigue" manner. It is well known that materials fail in a cyclic fatigue mode under a cyclic applied stress lower than that in a monotonic mode. We postulate that a lower fracturing pressure is required to disintegrate the tight material under cyclic (pulsation) loading. Under controlled pulsation process, the fractured zone may be more homogeneous rather than localized. The first stage of the research program involves experimentation in laboratory scale. In the second stage the test data will be used and implemented to feasibility studies of small-scale field experiments. The third stage is the development of novel technologies for exploitation of Montney Formation. This research program clearly carries both scientific and socio-environmental-economic impacts. Findings from this research program are readily transferred to research fields as listed above. Technology transfer and collaboration with industrial partners and regulators address public concerns, promote protection of the Environment, and enhance our economy and employment.

在工程应用中通常会遇到循环载荷。风在高建筑物上施加动态负载。波和冰负荷对北极水域的近海结构和运输基础结构构成威胁。降水和地下水位的季节性变化在土方工程上施加了重复的载荷。循环冻结地面以及交通负荷会影响人行道和掩埋公用事业的长期性能。自然地震和滑坡等天然地球岩本质上是循环和动态的。矿物采矿以及油和天然气提取也涉及周围环境的循环载荷。该拟议的研究计划的长期目标是开发技术来量化该领域遇到的循环负荷下不同地材料的疲劳行为和预期的寿命，以便可以开发出新的技术来预防危害，保护环境，优化材料寿命和自然资源范围和自然资源恢复。在这项拟议的研究中研究的第一类土地材料是蒙特尼形成，它是加拿大主要的天然石油和天然气资源之一。由于其紧密的孔结构，液压压裂（HF）已用于剥削该资源。它涉及将化学处理的液体高压注射到形成中，以创建一个破裂的网络，从而增强石油和天然气的产生。由于液压压裂引起的断裂液和碳氢化合物的污染，对天然水源的潜在风险引起了公众的关注。液压压裂还会引起地震事件，这可能会对地面设施构成不利影响。 迫切需要修改当前的HF处理，以增强这种紧密的材料中的液压流，并减少从治疗中释放的地震能量。我们建议通过以可控制的“疲劳”方式使其解锁紧密的材料。众所周知，在循环疲劳模式下，在循环施加的应力下，材料在单调模式下的循环疲劳模式失败。我们假设在循环（脉动）载荷下将紧密的材料分解为较低的断裂压力。在受控的脉动过程中，断裂区域可能更均匀而不是局部。研究计划的第一阶段涉及实验室规模的实验。在第二阶段，测试数据将用于小规模现场实验的可行性研究。第三阶段是开发用于剥削蒙特尼组的新技术。该研究计划显然带有科学和社会环境经济的影响。如上所述，该研究计划的发现很容易转移到研究领域。与工业合作伙伴和监管机构的技术转移和合作解决了公众关注，促进环境的保护，并增强我们的经济和就业。